Age Related Macular Degeneration (AMD) is a major blinding disease of the elderly in this country and, while VEGF inhibitors often stem the late, exudative stages of the disease, there is no effective therapy for the earlier, atrophic form of AMD. Oxidative damage to the retinal pigment epithelium (RPE) contributes to AMD by reducing the function of these cells and by stimulating an inflammatory cascade that leads to the pathologic hallmarks of the disease, localized atrophy of the retina and choroidal neovascularization. One source of the RPE- damaging reactive oxygen species (ROS) are the mitochondria of the RPE cells themselves. To determine whether mitochondria are an important source of ROS in the RPE in vivo, the SOD2 gene, encoding the protective enzyme MnSOD, will be deleted specifically in the RPE of mice, using a mouse line containing an allele of SOD2 flanked by loxP sites and RPE-specific expression of Cre recombinase. We plan 3 sets of experiments: (1) We will monitor the time course of retinal degeneration in real time in living mice using electrophysiology (ERG), high resolution structural analysis (SD-OCT) and behavioral analysis (Optomotry). In post mortem samples, we will examine morphological changes to the RPE, Bruch's membrane and the neural retina and to measure accumulation of lipofuscin in the RPE. We will induce the deletion of SOD2 both in neonatal and in adult mice to determine which approach better models human geographic atrophy. (2) We will increase mitochondrial oxidative stress by deletion of SOD2 in mice bearing a homozygous mutation in the gene for the transcription factor Nrl. These mice have a cone-only retina which may resemble the cone-rich human macula better than the normal mouse retina. By this means we hope to learn why the central retina is more sensitive to oxidative stress than the peripheral retina. (3) We will attempt to counteract mitochondrial oxidative stress by elevating a set of antioxidant enzymes, including heme oxygenase-1, glutathione transferases, and NAD(P)H:quinone oxidoreductase 1. These genes for these enzymes contain a common sequence component denoted "ARE" for antioxidant sequence element. We will stimulate this antioxidant response in two ways-by viral delivery of a gene that stimulates the response and by oral delivery of a novel drug that activates this pathway. We hope that these approaches may lead to a therapy for the atrophic form of AMD.